In recent years, thermal transfer systems have been developed to obtain prints from a color video camera. According to one way of obtaining such prints, an electronic picture is first subjected to color separation by color filters. The respective color-separated images are then converted into electrical signals. These signals are then operated on to produce cyan, magenta and yellow electrical signals Then the signals are transmitted to a thermal printer. To obtain the print, a cyan, magenta and yellow dye-donor element is placed face-to-face with a dye receiving element. The two are then inserted between a thermal printing head and a platen roll. A line-type thermal printing head is used to apply heat from the back of the dye-donor sheet. The thermal printing head has many heating elements and is heated up sequentially in response to the cyan, magenta and yellow signals. The process is then repeated for the other two colors. Further details of this process and an apparatus for carrying it out are contained in U.S. Pat. No. 4,621,271 by Brownstein entitled "Apparatus and Method For Controlling A Thermal Printer Apparatus," issued Nov. 4, 1986, the disclosure of which is hereby incorporated by reference.
Titanium alkoxides (such as Tyzor TBT.RTM. (titanium tetra-n-butoxide of duPont)) have been used as subbing layers between a polyester support and a dye-layer. While these materials are excellent subbing layers for adhesion purposes, problems have arisen with hydrolytic instability and they are difficult to coat in a reproducible manner. It has also been observed that degradation of dyes in the dye-donor can occur when titanium alkoxides are used as a subbing layer. This problem is particularly prevalent with arylidene pyrazolone yellow dyes. The subbing layers of the prior art may also have problems in that when a thin layer of polyester support is used for the dye-donor there is a greater tendency for layer delamination, particularly when multiple prints are attempted from a single donor.
U.S. Pat. No. 4,695,288 is directed to a dye-donor element for thermal dye transfer comprising a subbing layer comprising recurring units of an ethylenically unsatuated monomer and recurring units of an ethylenicaly unsatuated carboxylic acid.